The present invention relates to a low-pressure casing for a brake booster for use in automotive vehicles comprising two casing shells which are sealingly interconnected and each including a casing end wall and a substantially cylindrical circumferential section of the casing, and a circular reinforcement plate abutting the inner side of one of the casing end wall and fastened to a master brake cylinder or to the automotive vehicle by means of bolts.
In low-pressure brake boosters for automotive vehicles, the master brake cylinder is fastened to one casing end wall of the low-pressure casing, while the other end wall is fastened to the automotive vehicle, preferably to the splashboard. The brake forces which are transmitted onto the actuating piston of the master brake cylinder when braking will have to be re-transmitted as reaction forces from the master brake cylinder onto the point where the brake booster is fastened to the automotive vehicle. Taking into consideration that these comparatively high tension forces take their course via the low-pressure casing, the low-pressure casing has so far been designed with comparatively thick walls, which acts, however, adversely to a generally desired reduction of the brake booster's weight.
A substantial reduction in weight by a thin-walled low-pressure casing construction may be achieved by having the tension forces transmitted via separate tie elements, for instance, tie bolts (German Patent DE-OS No. 2,845,794) or via a central reinforcement tube which interconnects the two casing end walls (German Patent DE-OS No. 2,837,911). In any case, the sealing of the axially movable wall, at which the boosting force is generated, necessitates additional structural arrangements at the points where these tie elements extend through the movable wall and represents a possible source of failure.